System and method for lift augmentation of atmospheric entry vehicles during aerocapture and entry, descent, and landing maneuvers

ABSTRACT

A magnetohydrodynamic (MHD) flow control mechanism is described which substantially improves the existing processes in that smaller magnetic fields, requiring far less mass, are placed away from the forebody of the spacecraft to produce Lorentz forces that augment the lift and the drag forces for guidance, navigation, and control of the spacecraft.

CROSS-REFERENCE TO RELATED PATENT APPLICATION(S)

This patent application claims the benefit of and priority to U.S. Provisional Patent Application Ser. Nos. 63/178,720 entitled Method for Lift Augmentation of Atmospheric Entry Vehicles During Aerocapture and Entry, Descent, and Landing Maneuvers and 63/178,761 entitled Electrode Design for Lift Augmentation of Atmospheric Entry Vehicles During Aerocapture and Entry, Descent, and Landing Maneuvers, both filed on Apr. 23, 2021, the contents of which is hereby incorporated by reference in its entirety for any and all non-limiting purposes.

Additionally, reference is made to U.S. patent application Ser. No. ______ (Attorney Docket No. 20037-1), for Electrode Design for Lift Augmentation of Atmospheric Entry Vehicles During Aerocapture and Entry, Descent, and Landing Maneuvers, filed Apr. 22, 2022, which is incorporated herein by reference for any and all non-limiting purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention described herein was made in the performance of work under a NASA contract and by an employee/employees of the United States Government and is subject to the provisions of Public Law 96-517 (35 U.S.C. § 202) and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon or therefore. The contractor did not elect title in accordance with the provisions of 35 U.S.C. § 202.

BACKGROUND

In the continuing quest to explore and understand space, spacecraft design is of critical importance. Researchers continue to look for ways to improve spacecraft for long-duration scientific orbits around distant Solar System destinations without the need for heavy fuel loads which limit performance, mission duration, and mass available for science payloads.

The process of aerocapture has become a process of particular interest as a near fuel-less option for orbit insertion. The aerocapture process primarily relies on a planet's (or other celestial body's) atmosphere to achieve orbit, wherein the aerodynamic drag generated as the spacecraft enters the atmosphere slows the spacecraft and allows for it to be captured by the planet. During this pass through the atmosphere, significant thermal energy is created. Accordingly, the spacecraft must be protected from this extreme heat. The spacecraft require thermal protection systems, such as aeroshells, which encase the spacecraft in a protective shell.

Blunt body aeroshells offer the best decelerators but are constrained by the amount of lift that can be created by a blunt body aeroshell shape for maintaining course during entry trajectories and prescribed flight corridors. Changing in flight the center of gravity via mass ballast and changing the center of pressure via trim tabs can increase lift (for the blunt body aeroshells) but not sufficient for entries at Neptune and other worlds with atmospheres. As determined in the 2004 Neptune study with a summary of findings published in NASA's April 2006 document entitled Aerocapture Systems Analysis for a Neptune Mission which is incorporated herein by reference in its entirety for any and all non-limiting purposes, the tight entry corridor at Neptune requires an aeroshell shape capable of L/D (Lift-to-Drag) ratios around 0.8. Blunt body aeroshells generally provide a L/D ratio of around 0.2. Hence, that study selected a Mid L/D shape capable of achieving the higher L/D ratio. A key finding of that 2004 Neptune study is that the “[thermal protection system] TPS thicknesses are beyond current manufacturing experience for carbon phenolic for this shape and acreage.” The Mid L/D concept described in the 2004 Neptune study suggests a complex system of structure and instruments that are integrated into a launch vehicle that is much longer than necessary but required to meet the diameter of the Mid L/D concept determined for Neptune. The Mid L/D concept was able to deliver about 40% more mass to Neptune orbit than an all propulsive approach. However, that Mid L/D aerocapture mission concept still required over 10 years of cruise time to reach Neptune. These factors offered motivation for studying a new approach for a spacecraft capable of entering Neptune's atmosphere which provides improvements in, e.g., trip time, net mass delivered, entry velocity vs. flight time.

Previous studies have explored the use of magnetic forces to control the flow near the forebody of an aeroshell during re-entry for reducing the thermal loads on the spacecraft. The principles of magnetohydrodynamic (MHD) flow control mechanisms were first extended to the practice of EDL (planetary Entry, Descent, Landing) at Mars about 20 years ago. The basis for the initial study resided in the recognition that the electron number densities observed in aerothermal analysis results for Mars entries were similar orders of magnitude as those required for MHD power generation practices on Earth. Hence, the preliminary work for Mars entries looked to harvest electrical power from the ionized flow occurring during the hypersonic entry phase at Mars. The initial study also looked at harvesting the atmosphere of Mars, especially oxygen, that was dissociated from the 96% carbon dioxide atmosphere by the elevated temperatures and pressures occurring during the hypersonic entry. It was suggested at that time that harvesting electricity from the flow field would likely produce Lorentz Forces that could be used to steer the spacecraft. A decade after this initial work, NASA funded a Fellowship PhD program to explore the creation of MHD drag forces at Mars for extending the prior foundational research. That research further demonstrated that electrical current could be harvested and MHD drag forces could be produced under simulated Martian entry conditions. The results of this research are described in Ali, H., Magnetohydrodynamic Energy Generation and Flow Control for Planetary Entry Vehicles, Doctoral Dissertation, Georgia Institute of Technology, August 2019, which is incorporated herein by reference in its entirety for any and all non-limiting purposes.

The goal, illustrated in prior art FIG. 1, is to push the bow shock layer away from the spacecraft for reducing the heat reaching the forebody surface of the spacecraft. As shown in FIG. 1, magnetic dipole (e.g. a current loop) and ionized gas crossing the B field lines creates a circular current and thus Lorentz forces pushing the bow shock upstream. With the increased shock stand-off distance there is reduced peak heat flux. But, in order to increase the bow shock standoff distance, large magnetic fields are required, which therefore requires massive magnet(s) placed near the forebody of the spacecraft, greatly limiting its feasibility.

Accordingly, for these and other reasons, there continues to be a need in the art for improved spacecraft design and operation for use in exploring planets and celestial bodies.

BRIEF SUMMARY

In a first non-limiting embodiment, a magnetohydrodynamic (MHD) flow control system for use with an aeroshell of a spacecraft includes: at least a first pair of electrodes placed on a first predetermined portion of an outward facing surface of the aeroshell; and a magnet placed on a second predetermined portion of an inward facing surface of the aeroshell, wherein the first predetermined portion and the second predetermined portion are at the same location, on opposing surfaces of the aeroshell.

In a second non-limiting embodiment, an aeroshell for use with a spacecraft includes: a blunt-body configuration; and at least one magnetohydrodynamic (MHD) flow control patch for producing Lorentz forces that augment lift and the drag forces for assisting with at least one of guidance, navigation, and control of the spacecraft, the at least one MHD flow control patch including, at least a first pair of electrodes placed on a first predetermined portion of an outward facing surface of the aeroshell; and a magnet placed on a second predetermined portion of an inward facing surface of the aeroshell, wherein the first predetermined portion and the second predetermined portion are at the same location, on opposing surfaces of the aeroshell.

In a third non-limiting embodiment, a magnetohydrodynamic (MHD) flow control system for use with an aeroshell of a spacecraft includes: multiple pairs of electrodes placed on a first predetermined portion of an outward facing surface of the aeroshell, wherein the multiple pairs of electrodes are arranged in a stacked configuration; and at least one magnet placed on a second predetermined portion of an inward facing surface of the aeroshell, wherein the first predetermined portion and the second predetermined portion are at the same location, on opposing surfaces of the aeroshell.

These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a prior art illustration of the desired result from implementation of an embodiment described herein;

FIG. 2 is a prior art illustration summarizing the physics principles behind implementation of an embodiment described herein;

FIGS. 3a, 3b, 3c, 3d illustrates various views of an MHD patch implemented in accordance with an embodiment described herein;

FIGS. 4a and 4b illustrate various views of an MHD patch implemented in accordance with an embodiment described herein;

FIGS. 5 illustrates an MHD patch implemented in accordance with an embodiment described herein;

FIG. 6 shows the Lorentz Forces (F_(x), F_(y), F_(z)) on a blunt body aeroshell in the presence of ionized flow in accordance with an embodiment described herein;

FIG. 7 shows effects of magnetic field orientation on the Lorentz forces and energy values of the MHD approach applied to a specific use case in accordance with an embodiment described herein;

FIG. 8 shows the resulting Lorentz forces in accordance with the magnetic field orientations of FIG. 7;

FIG. 9 illustrates the effect of distance between electrodes on the current density streamlines in accordance with an embodiment described herein;

FIG. 10 shows the resulting force values in accordance with the distance between electrodes of FIG. 9;

FIGS. 11a, 11b, 11c are schematics of a prior art mid L/D aeroshell used in the analysis of the MHD approach of the embodiments described herein;

FIG. 12 illustrates the location of the mid L/D aeroshell which was selected for analysis of the MHD approach of the embodiments described herein as applied to a first specific use case; and

FIG. 13 illustrates the location of the mid L/D aeroshell which was selected for analysis of the MHD approach of the embodiments described herein as applied to a second specific use case.

DETAILED DESCRIPTION OF EMBODIMENTS

The MHD approach in embodiments may substantially improve the existing processes in that smaller magnetic fields, requiring far less mass, are placed away from the forebody of the spacecraft to produce Lorentz forces that augment the lift and the drag forces for guidance, navigation, and control of the spacecraft, as explained herein. The Embodiments described below facilitate lift generation for enabling the use of blunt bodies and other aeroshell shapes to meet stringent entry parameters for several mission destinations of interest to humanity, including Neptune and Mars.

It has been documented and well understood how the principles of MHD could be applied to entry bodies to reduce thermal stresses on the aeroshell as well as to augment drag and to harvest atmospheric gases and to generate electrical power.

MHD Theory for EDL Applications

As shown in the schematic of FIG. 2, the principles of MHD stem from the theory of electrical currents flowing in the presence of a magnetic field. In this case, the electrical current flow is created when the conductivity of the planet's (or other celestial body's) atmosphere is sufficient to facilitate current flow between electrodes with opposite polarity that are placed on the outer surface of the spacecraft. Hence, the conductivity of the flow is critical to the use of this MHD approach during atmospheric entries.

When electrically conducting fluid crosses magnetic field lines, charged particles experience Lorentz forces {right arrow over (F)}_(L)=q{right arrow over (u)}×{right arrow over (B)}, and since the charges of electrons and ions are of opposite signs, the electrons and ions are pulled apart, which creates a Faraday electromotive force (emf). If the circuit is closed, current flows:

j=(1−K)σuB_(z)   (1)

Here σ is the electrical conductivity, and K is the load factor (load resistance vs plasma resistance). Interaction of the induced current with the B field creates body force per unit area:

{right arrow over (F)}={right arrow over (J)}×{right arrow over (B)}  (2)

If the B field is inclined with respect to the surface, the force would have both decelerating(drag) and normal (lift) components:

F _(x)=−(1−K)σuB_(z) ²   (3)

F _(z)=(1−K)σuB_(z) B _(x)   (4)

The scalar electrical conductivity is proportional to the number density n_(e) of principal charge carriers (electrons) and inversely proportional to the rate, or frequency, of their collisions with ions (v_(ei)) and neutral molecules (v_(en)):

$\begin{matrix} {\sigma = \frac{e^{2}n_{e}}{m\left( {v_{ei} + v_{en}} \right)}} & (5) \end{matrix}$

Here e and m are the electron charge and mass, respectively. At low ionization fraction

$\frac{n_{e}}{n} \leq {10^{- 3} - 10^{- 2}}$

(n is the number density of gas), electrons collide mostly with neutral molecules, and the conductivity is proportional to the ionization fraction:

$\begin{matrix} {\sigma \approx {3 \times 10^{5}\frac{n_{e}}{n}{S/m}}} & (6) \end{matrix}$

In this regime, the conductivity in hypersonic shock and boundary layers reaches ˜10-100 S/m. At high ionization fraction

${\frac{n_{e}}{n} \leq {10^{- 3} - 10^{- 2}}},$

electrons collide mostly with ions, and the conductivity does not depend on the ionization fraction, instead being determined by the electron temperature:

σ≈const ×T _(e) ^(3/2)   (7)

In this regime, the conductivity reaches ˜1000-3000 S/m.

Hall Effect

With the induced electric field E perpendicular to the B field, electrons and ions have {right arrow over (E)}×{right arrow over (B)} drift motion along the flow, which effectively diverts their cross-low motion and thus reduces MHD body forces. This can be expressed as an effective conductivity lower than the scalar one.

Ion Slip Effect

MHD effects increase with flow velocity. However, as B field increases, the motion of electrons and ions is retarded so much that the ion-electron fluid starts to slip against the bulk neutral gas, and the lower ion-electron velocity reduces the MHD effects (including body forces). This ion slip effect can also be expressed as a reduction in the effective conductivity.

$\begin{matrix} {\sigma_{eff} = \frac{\overset{\sim}{\sigma}}{1 + {\overset{\sim}{\Omega}}^{2}}} & (8) \end{matrix}$

Here the conductivity {tilde over (σ)} and the Hall parameter {tilde over (Ω)} corrected for ion slip are:

$\begin{matrix} {{\overset{\sim}{\sigma} = \frac{\sigma}{1 + {\Omega_{e}\Omega_{i}}}};{\overset{\sim}{\Omega} = \frac{\Omega_{e}}{\Omega_{e}\Omega_{i}}}} & (9) \end{matrix}$

Here σ is the scalar conductivity, and the electron and ion Hall parameters are:

$\begin{matrix} {{\Omega_{e} = \frac{eB}{m\left( {v_{ei} + v_{en}} \right)}};{\Omega_{i} = \frac{eB}{{Mv}_{in}}}} & (10) \end{matrix}$

(M and v_(in) are the ion mass and ion-neutral collision frequency, respectively).

The performance-reducing Hall and ion slip effects become dominant when the Hall parameter (the product of the electron mobility and the magnetic field) is high, which occurs when the magnetic field is high and the gas density is low. However, these effects can be exploited for modulating axisymmetric forces and moments, as will be illustrated later in one case presented for Mars.

For embodiments described herein, NASA Langley's CFD code LAURA is used to calculate properties of the flow field around an entry aeroshell. A description of LAURA may be found in Thompson, K., et al., LAURA User's Manual: 5.6, NASA TM 2020-220566, 2020. These calculated properties may then fed into MHD plasma code CFDWARP to calculate MHD properties of the flow and estimate Lorentz forces generated and electrical power available on a local region of the aeroshell during that entry condition. The CFDWARP code has been described in the prior art at, for example, B Parent, et al., Modeling Weakly-Ionized Plasmas in Magnetic Field: A New Computationally-Efficient Approach, Journal of Computational Physics, Vol. 300, Pages 779-799, 2015, which is incorporated herein by reference in its entirety for any and all non-limited purposes.

In one embodiment, an MHD patch effector device is integrated with a blunt-body aeroshell for generating Lorentz forces as shown in FIGS. 3a, 3b, 3c and 3d . In one embodiment, the MHD patch effector consists of: 1) a pair of electrodes 10 a, 10 b placed on the surface of the aeroshell 5 at a prescribed distance apart and 2) a magnet 15 placed just below the aeroshell's outer surface, with the magnetic field (B) protruding out of the surface. The electrodes can be formed from any materials that can handle high temperatures and are still electrically conductive, such as Tungsten and Tungsten alloys. The magnet 15 could be a permanent magnet(s) or electromagnet(s), e.g., coil, self-powered by the electrical energy harvested from the flow or powered by another energy source. FIG. 3a shows the front view of the aeroshell 5 with (+/−) electrodes 10 a, 10 b thereon. FIG. 3b is a side, cross-sectional view of FIG. 3a , wherein the aeroshell 5 with electrode 10 b is shown, as well as the magnet 15 on the inside of the aeroshell, opposite the electrodes on the outside of the aeroshell. FIG. 3b also includes direction indicators for the magnetic field (B), Flow of air, plasma around the aeroshell and electrodes (Flow) and spaceship velocity vector vs and force (F). FIGS. 3c and 3d offer alternative views of the MHD patch effector device with directional indicators for magnetic field (B), (Flow), force (F) and current density (J), wherein: F=J×B.

In an alternative embodiment, F can be redirected by clocking (rotating) the electrode pair since the electrode pair prescribes the orientation of the current flow vector J based on the electrical conductivity of the ionized Flow. FIGS. 4a and 4b show two different electrode configurations as viewed from the same front view outside of the aeroshell and provide an indication of change in direction of F₁ or F₂ force vectors dependent upon the orientation of the electrode pair (10 a, 10 b). The force vector F₂ in FIG. 4b has components that produce drag and lift as well as rolling moment, whereas the force vector F₁ in FIG. 4a has components that product drag and lift only. The clocking capability offers a side force that can be used to spin or control the spin of the spacecraft and allows the spacecraft to counteract side forces, e.g., Hall effect and ion slip effect, generally produced during entries in very low density atmosphere.

While only a single example of clocking position is illustrated, one skilled in the art with the benefit of this disclosure will appreciate that the electrode pair (10 a, 10 b) may be controlled to clock to any required position around a central axis by any control means, e.g., mechanical, electro-mechanical, etc.

FIG. 5 illustrates an embodiment wherein multiple electrode pairs, P₁, P₂, P₃, are overlaid (e.g., stacked) and each individual pair can be alternately or concurrently turned on or activated by electrical loop closure. The ability to switch the pairs on and off allows for controlling the F vector and components of drag, lift, and rolling moment directions in order to steer a spacecraft. Upon review of this disclosure, one skilled in the art will appreciate that the number and orientation of electrode pairs is not limited to the 3 shown in FIG. 5. Any number of electrode pairs could be used to achieve the force component magnitudes and orientations deemed necessary by engineering analysis to steer the spacecraft.

FIG. 6 shows the Lorentz Forces (F_(x), F_(y), F_(z)) on a blunt body aeroshell in the presence of ionized flow. For an initial case, the MHD results are as follows. Force on the gas by the electromagnetic fields (J×B)=(−2718, −103, +103) Newtons (N). That represents a force of 2718 N in the direction opposite of the “bulk” flow, a force of 103 N that acts normal to the surface that is pressing on the surface, and a force of 103 N that acts tangential to the surface and perpendicular to the “Bulk” flow direction and perpendicular to the surface normal direction. Whether the force in the X-axis acts as drag depends on the orientation of the modeled aeroshell surface to the velocity vector of the spacecraft. Likewise, whether the force in the Y-axis acts as lift and the force in the Z-axis acts as a rolling moment depends on the orientation of the modeled aeroshell surface to the velocity vector of the spacecraft. For instance, if the modeled aeroshell is located on the underbelly of the mid L/D vehicle (see FIG. 12), then these X-, Y-, and Z- forces can be considered drag, lift, and roll, respectively. However, if these X-, Y-, and Z- forces are acting along an aeroshell representative of a 70-degree cone, then the X-axis force is acting more like a lift force than a drag force, and the Y-axis force is acting more like a drag force than a lift force, while the Z-axis force is representative of a rolling force. Further to the initial example, the rate of energy input to the gas by the electromagnetic fields (E*J)=−3.01 Megawatts; the rate of work done by the electromagnetic fields (V*(J×B))=−29.2 Megawatts; and the rate of heat deposited to the gas by electromagnetic fields (Energy input−work done)=26.2 Megawatts.

Additional cases were run for understanding the effects of magnetic field orientation on the Lorentz Forces and Energy values of the MHD approach applied to the Neptune entry case of 29.24 km/s at an atmospheric density of 1.45e−4 kg/m3. A value of 1 Tesla was used for these additional cases. Shown in FIG. 7, the orientation of the magnetic field varied in the X-Y plane for 180 degrees (θ=−90 to +90 degrees). The magnetic field remained orthogonal to the Z-axis for these additional cases.

The resulting Lorentz Forces are illustrated in FIG. 8 for the values of θ between −90 degrees and +90 degrees. The force in the Y-axis (perpendicular to the aeroshell surface) is maximal when θ=+/−45 degrees (F_(emfield,y)). The force in the X-axis (“bulk” flow direction) is maximal when θis +/−90 degrees (F_(emfield,x)).

A force of 4000 Newtons in these cases translates in an electromagnetic force per surface area of 200 kN/m2. Therefore, an MHD patch effector having an area of 1 m² would produce a force of 2.0e+5 N. That value is the same order of magnitude as the “whole body” drag and lift forces computed by LAURA for the Neptune entry velocity and atmospheric density. The math comes down to the sizing and orientation of the magnetic field to produce the desire drag and lift vectors for controlling the entry body. The entry body could be a number of shapes, possibly including a 70-degree cone.

The distance between the two electrodes (D) (See FIG. 3a ) was varied between 0.07 meters and 0.97 meters. Zero current boundary conditions were imposed everywhere except at the two electrodes. Both electrodes were given the same voltage (short circuit). Flow properties are frozen to represent no coupling. Hall effect and ion slip effects are taken into consideration.

The effect of distance between electrodes on the current density streamlines is illustrated in FIG. 9. The longer streamlines (SL) represent the case for D=0.97 meters spacing while the shorter streamlines (Ss) represent the case for D=0.07 meters.

The effect of electrode spacing (D) (See FIG. 3a ) on Lorentz forces is shown in FIG. 10. Force increases when the electrode spacing is increased. This effect is due to longer length of the current streamlines being more perpendicular to the flow and the magnetic field as D is increased. For instance, the shape of the shorter streamlines S_(s) for the shorter spacing look more circular when compared to the much longer streamlines S_(L) for the wider spacing.

Hence, a longer portion of the S_(L) streamlines, which represent J, are orthogonal to the B-field than the portion of the shorter streamlines S_(s).

The force values (shown in FIG. 10) reach up to 800 kN/m2. Hence, a “MHD patch” that encompasses 1 m² of the aeroshell can, theoretically, produce up to 800 kN force. That value is not only the same order of magnitude but also exceeds the value computed by LAURA. Hence, the L/D ratio exceeds 1.0 for this situation. This is a ground-breaking discovery for missions, such as but not limited to Neptune. And performance during atmospheric entries at Earth, such as return from the Moon or return from Mars, is expected to be similar to this Neptune case.

The following paragraphs provide further support of the description and embodiments discussed above with respect to particular missions, i.e., Neptune and Mars, and as such, should not be construed as limiting examples.

The criteria used to select a region of flow along the spacecraft for further analysis are derived from the principles of MHD illustrated above in FIG. 2. In this example, conductivity is the most important criteria. As explained above, conductivity is dependent on temperature and density conditions of the flow field near the surface of the vehicle. A second criteria for this example is the velocity of the flow in terms of magnitude and direction for establishing the location and placement of the electrodes. A third criteria in this example is the geometric orientation of the magnetic (B-) field with respect to the current flow to produce Lorentz forces with axis components in the orthogonal coordinate system that are in the “drag direction” and “lift direction” and “rolling moment” direction.

The LAURA Navier-Stokes solver was applied for the baseline Mars and Neptune flowfields considered in embodiments described herein. Two-temperature thermochemical nonequilibrium was assumed, where the chemical kinetics for the Mars case are taken from Johnston and Brandis, Modeling of Nonequilibrium CO Fourth-Positive and CN Violet Emission in CO2-N2 Gases, Journal of Quantitative Spectroscopy and Radiative Transfer, Vol. 149, 2014, pp. 303-317 and for the Neptune case from a combination of Park, C. “Nonequilibrium Ionization and Radiation in Hydrogen Helium Mixtures”, Journal of Thermophysics and Heat Transfer, Vol. 26, No. 2, 2012, pp. 231-243, Gocken, T., “N2-CH4-Ar Chemical Kinetic Model for Simulations of Atmospheric Entry to Titan,” Journal of Thermophysics and Heat Transfer, Vol. 21, No. 1, 2007, pp. 9-1, Fujita K, Yamada T, and Ishii N., “Impact of Ablation Gas Kinetics on Hyperbolic Entry Radiative Heating,” AIAA Paper 2006-1185, 2006, and Johnston and Brandis. All references are incorporated herein by reference. The wall was assumed fully catalytic and in radiative equilibrium. The solution and grid convergence criteria applied were consistent with the state-of-the-art applied for NASA flight programs.

For the Neptune case, the aerothermal analysis and other mission results of the 2004 Neptune study were reviewed for the mid L/D aeroshell shown in FIGS. 11a (top view), 11 b (side view) and 11 c (aft view). The location selected LA_(N) for further analysis is shown in FIG. 12 based on the criteria stated above. The entry conditions used in the 2004 Neptune study were selected as an illustrative embodiment.

For the Mars case, the team reviewed several mission cases and selected a blunt body aeroshell. The location LA_(M) selected for further analysis is shown in FIG. 13 based on the criteria stated above. However, for Mars, a higher entry velocity representing a faster flight to Mars was selected.

For the Neptune entry, a two-temperature thermochemical nonequilibrium flow field was modeled in LAURA for the geometry from Edquist, Karl T., et al., “Configuration, Aerodynamics, and Stability Analysis for a Neptune Aerocapture Orbiter,” AIAA 2004-4953, AIAA Atmospheric Flight Mechanics Conference and Exhibit, 16-19 Aug. 2004, Providence, R.I., L/D=0.8, 40 degrees Angle of Attack, 29.24 km/s entry velocity at an atmospheric density of 1.45e−4 kg/m3. Free-stream mass fractions of 0.6246 H2, 0.2909 He, and 0.0846 CH4 were used. The species included in the simulation are H2, H, H+, He, He+, e-, CH4, CH3, CH2, CH, C2, C, and C+. Temperature, pressure, and electron number densities were calculated. For the 29 km/s Neptune case, the “whole body” drag=5.6487e+05 N and lift=4.4911e+05 N. An additional case was run in LAURA for comparison to the 2004 case. For the 35 km/s Neptune case, the “whole body” drag=8.3943e+05 N and lift=6.5381e+05 N.

For the Mars entry, a two-temperature thermochemical nonequilibrium flow field was modeled in LAURA to represent a HIAD at 0 degrees Angle of Attack, 9 km/s entry velocity at an atmospheric density of 4.4e-5 kg/m3. Free-stream mass fractions of 0.97 CO2 and 0.03 N2 were used. The species included in the simulation are CO2, N2, CO, NO, O2, CN, C2, C, N, O, N2+, CO+, NO+, C+N+, O+, and e-. Temperature, pressure, and electron number densities were calculated. The HIAD geometry consists of a 70-degree sphere-cone with a 10-meter nose radius, 17.2-meter maximum diameter, and an 0.35-meter shoulder radius. The “whole body” drag value of 7.0887e+05 N was calculated by LAURA for the Mars case at 9.0 km/s, 4.4e−5 kg/m3. Additional Mars cases were run in LAURA for comparison.

At 7.5 km/s, 4.4e−5 kg/m3: Drag=4.9227e+05 N. At 9.0 km/s, 4.4e-4 kg/m3: Drag=7.0887e+06 N. At 7.5 km/s, 4.4e−4 kg/m3: Drag=4.9227e+06 N.

One skilled in the art will appreciate that while the embodiments herein are generally directed to a single MHD patch, the embodiments are not so limited. Multiple patches having different configurations, e.g., dimensions, electrode spacing, electrode material, etc., may be utilized on an aeroshell in accordance with expected environment. Such alternatives are considered to be well within the scope of the embodiments.

The performance of the “MHD Patch” for Earth entries such as aerocapture missions returning from the Moon or from Mars is expected to be very similar to the large lift forces shown for the Neptune cases illustrated herein.

It is to be understood that the novel concepts described and illustrated herein may assume various alternative configurations, except where expressly specified to the contrary. It is also to be understood that the specific systems, devices and processes illustrated in the attached drawings, and described herein, are simply exemplary embodiments of the embodied concepts defined in the appended claims. Accordingly, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.

Reference in the specification to “one embodiment” or to “an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment. The appearance of the phrases “in one embodiment,” “in some embodiments,” and “in other embodiments” in the specification are not necessarily all referring to the same embodiment or the same set of embodiments.

As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, system or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. Additionally, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the invention. This detailed description should be read to include one or at least one and the singular also includes the plural unless it is obviously meant otherwise. 

We claim:
 1. A magnetohydrodynamic (MHD) flow control system for use with an aeroshell of a spacecraft comprising: at least a first pair of electrodes configured for placement on a first predetermined portion of an outward facing surface of the aeroshell; and a magnet configured for placement on a second predetermined portion of an inward facing surface of the aeroshell, wherein the first predetermined portion and the second predetermined portion are at the same location, on opposing surfaces of the aeroshell.
 2. The system of claim 1, wherein the magnet is selected from the group consisting of a permanent magnet and an electromagnet.
 3. The system of claim 1, wherein the electrodes are formed of at least one of tungsten and a tungsten alloy.
 4. The system of claim 1, wherein the at least a first pair of electrodes is rotatable around a central axis by a control mechanism.
 5. The system of claim 1, further comprising at least a second pair of electrodes stacked on the first pair of electrodes, wherein individual electrodes from each of the first and second pair of electrodes do not overlap.
 6. The system of claim 1, further comprising at least a second pair of electrodes stacked on the first pair of electrodes, wherein individual electrodes from each of the first and second pair of electrodes partially overlap.
 7. The system of claim 1, wherein the system comprises the aeroshell, and the aeroshell is a blunt-body aeroshell.
 8. The system of claim 1, wherein a distance between each individual electrode in the first pair of electrodes is between 0 and 1 m.
 9. The system of claim 1, wherein the system is configured to encompasses approximately 1 m² of an aeroshell.
 10. An aeroshell for use with a spacecraft comprising: a blunt-body configuration; and at least one magnetohydrodynamic (MHD) flow control patch for producing Lorentz forces that augment lift and the drag forces for assisting with at least one of guidance, navigation, and control of the spacecraft, the at least one MHD flow control patch including, at least a first pair of electrodes placed on a first predetermined portion of an outward facing surface of the aeroshell; and a magnet placed on a second predetermined portion of an inward facing surface of the aeroshell, wherein the first predetermined portion and the second predetermined portion are at the same location, on opposing surfaces of the aeroshell.
 11. The aeroshell of claim 10, wherein with the at least one MHD flow control patch, the Lift-to-Drag ratio of the spacecraft is greater than 1.0.
 12. The aeroshell of claim 10, wherein the magnet is selected from the group consisting of a permanent magnet, an electromagnet, and combinations thereof.
 13. The aeroshell of claim 10, wherein the electrodes are formed of at least one of tungsten and a tungsten alloy.
 14. The aeroshell of claim 1, wherein a distance between each individual electrode in the first pair of electrodes is between 0 and 1 m.
 15. The aeroshell of claim 10, wherein the system encompasses approximately 1 m² of the aeroshell.
 16. A magnetohydrodynamic (MHD) flow control system for use with an aeroshell of a spacecraft comprising: multiple pairs of electrodes placed on a first predetermined portion of an outward facing surface of an aeroshell, wherein the multiple pairs of electrodes are configured to be arranged in a stacked configuration; and at least one magnet configured to be placed on a second predetermined portion of an inward facing surface of the aeroshell, wherein upon placement of the electrodes and the at least one magnet, the first predetermined portion and the second predetermined portion are configured to be the same location, on opposing surfaces of an aeroshell.
 17. The system of claim 16, wherein the at least one magnet is selected from the group consisting of a permanent magnet, an electromagnet, and combinations thereof
 18. The system of claim 16, wherein the electrodes are formed of at least one of tungsten and a tungsten alloy.
 19. The system of claim 16, wherein individual electrodes from each of the multiple pairs of electrodes at least partially overlap.
 20. The system of claim 16, wherein the system is configured that such when properly placed on an aeroshell, the system encompasses approximately 1 m² of the aeroshell. 